Abstract

Montetrisaite, a new hydroxy-hydrated copper sulfate mineral species from Monte Trisa, Torrebelvicino, Vicenza, in Italy, has chemical formula Cu6(SO4)(OH)10·2H2O. It is associated with galena, sphalerite, chalcopyrite, cerussite, anglesite, goethite, langite, posnjakite, linarite and redgillite. The crystals are blue, vitreous, transparent, striated vertically, with a cleavage, {001}. The diffraction pattern shows strong reflections pointing to an orthorhombic unit-cell with a 2.989(2), b 16.970(5), c 14.812(4) Å, space group Cmc21, Z = 2. The strongest reflections [d in Å(Irel)(hkl)] are: 7.45(100)(002), 3.73(35)(004), 2.788(18)(061), 2.503(14)(132) and 1.595(20)(175). In addition, very weak and diffuse reflections occur, which point to a monoclinic cell with a doubled a parameter. The crystal structure is built up of layers of edge-sharing Jahn–Teller-distorted Cu-centered octahedra, to which single SO4 groups are connected on one side. Between the layers, H2O molecules are located, and the layers are connected through hydrogen bonds. The refined average structure shows sulfate groups and H2O molecules in both their statistically possible positions; in the real structure, however, only one half of those positions can be really occupied. The new mineral is structurally related to posnjakite, wroewolfeite, langite, and spangolite. On the other hand, its structure is significantly different from that of redgillite Cu6(SO4)(OH)10·H2O, which has a very similar chemical formula.